TOKYO—Among the unusual features of Japan’s justice system that have emerged in the
Carlos Ghosn
case, add this one: Prosecutors can seize and examine his communications with his lawyers, likely without consequences.

When Mr. Ghosn, the former chairman of
Nissan Motor Co.
, was arrested again over fresh suspicions on April 4, Japanese prosecutors confiscated communications with his overseas lawyers in a raid of his Tokyo apartment, said lead defense lawyer
Junichiro Hironaka.

The things prosecutors took “were mainly materials for his trial,” Mr. Hironaka said. “This clearly violates his right to defense and a fair trial.”

He said Wednesday that he has protested the action to prosecutors in a joint letter with Mr. Ghosn’s lawyers in the U.S., France and Lebanon. Mr. Hironaka said he also planned to ask a court to order the return of the materials.

In an interview last week, Mr. Ghosn’s wife, Carole, called the search “scary as hell” and she said she declined prosecutors’ request to question her about her husband’s case. She flew the next day to France. However, a Ghosn family representative said Wednesday that Mrs. Ghosn has returned to Japan and is planning to voluntarily answer questions at the Tokyo District Court on Thursday.

Carlos Ghosn, the former chairman of Nissan and Renault, assailed Nissan executives and said he is innocent, in a video released by his lawyers and was recorded before his arrest. Image: Getty Images

Japanese authorities said the seriousness of the new suspicions against Mr. Ghosn justified his latest arrest and the search, but other legal systems would see the confiscated communications as a violation of attorney-client privilege.

In the U.S., “the view is that a defendant can only adequately prove his or her innocence through the ability to communicate all information with his or her attorney without fear that would be disclosed,” said Nobuhisa Ishizuka, a lecturer at Columbia Law School and head of its Japanese legal-studies program. He added that if a U.S. judge thinks evidence was collected in violation of the privilege, prosecutors wouldn’t be able to use it in court.

The seizure is the latest instance in which Japan’s justice system has contrasted with other developed democracies since Mr. Ghosn’s initial arrest Nov. 19. As is common in criminal cases, Mr. Ghosn was held for weeks without charge after that arrest and interrogated by prosecutors without a lawyer present. After he was indicted, he was held for months in jail, although his alleged offense was nonviolent.

Mr. Ghosn says he is innocent of charges that include abusing his position at Nissan for private gain.

Lack of attorney-client privilege has now emerged as another issue for Mr. Ghosn. Lawyers said there is no law broadly protecting the privilege in Japan, although defendants have a general right to defend themselves in court and lawyers’ offices can’t be raided.

Ghosn Case

“I wonder if there are any other advanced countries that violate attorney-client privilege to such a large extent,” said Kaku Imamura, a criminal defense lawyer.

Prosecutors have declined to discuss details of Mr. Ghosn’s case but say they are handling it appropriately in accordance with the law. A Justice Ministry official blasted U.S. critics of Japan, saying they were ignorant of the limitations Japanese authorities face in gaining evidence by subpoena, wiretap or undercover investigation—all common methods in the U.S.

“Most of the things you probably see on U.S. television series, in terms of investigative methods, we can’t do,” the official said. “The only investigative method we really have is search and seize.”

Prosecutors rummaged through Mr. Ghosn’s apartment on April 4 as Mrs. Ghosn looked on. In addition to seizing documents Mr. Ghosn was preparing for his trial and the couple’s diaries, prosecutors took Mrs. Ghosn’s cellphones and Lebanese passport, according to the defense lawyer and Mrs. Ghosn.

When prosecutors obtain a warrant authorizing them to seize evidence, they generally interpret it broadly and take any item that could be relevant to the case, including family members’ possessions, lawyers said.

Even if a court decides later that prosecutors went too far, they probably won’t face consequences. “The hurdle is very high for evidence, even if it is collected illegally, to be excluded,” said Kenichi Nagai, a lawyer specializing in criminal cases. “The court often accepts improperly collected evidence, saying it’s not significant enough to exclude from evidence.”

The Japan Federation of Bar Associations has lobbied the Ministry of Justice and lawmakers to establish principles protecting the confidentiality of consultations between lawyers and their clients.

“Fears that information might be leaked make defendants hesitant to tell their lawyers unfavorable facts, although lawyers need to know all the facts, including negative factors, to make their defense plans,” said Tatsu Katayama, a lawyer who heads the federation’s working group on this issue.

One precedent suggests there might be a limit for Japanese prosecutors. In 2010, prosecutors raided the detention cell of a defendant in a burglary case in Osaka and confiscated letters he wrote to his lawyer. An Osaka court later found it was illegal and ordered the country to pay the defendant and his lawyer about $5,000 each.

Nonetheless, the defendant was convicted at trial.

Yasuhiko Miyashita, the defense lawyer in the case, said the raid had a psychological impact on his client and tilted the trial against him. Mr. Miyashita isn’t involved in the Ghosn case but said the facts there “look substantially the same to me.”

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